This invention relates generally to time modulation and more particularly to a system for continuous-time modulation.
Continuous-time modulators conventionally require the use of an analog-to-digital converter. Analog-to-digital converters have been designed in a variety of architectures. Conventionally, these architectures have been implemented with transistors. For example, one common implementation includes a cross-coupled pair of transistors. However, there are several disadvantages associated with using transistors to implement an analog-to-digital converter.
First, components used in digital circuits are becoming smaller and smaller. As these components decrease in size, quantum mechanical effects begin to influence the circuit performance. The electrical properties of conventional transistors may be altered in an unacceptable way by the quantum mechanical effects. Secondly, a transistor-implemented analog-to-digital converter is limited by the switching speed of the transistors, which may be too slow for some applications. Finally, conventional transistors are limited to two stable states. Thus, systems using transistors typically convert analog signals into binary digital signals, making the use of multi-valued logic difficult.
In accordance with the present invention, a system for continuous-time modulation is provided that substantially eliminates or reduces the disadvantages or problems associated with previously developed systems. In particular, the present invention provides a system for continuous-time modulation to quantize an analog signal without the use of transistors.
In one embodiment of the present invention, a continuous-time modulator is provided that comprises a modulator bridge having a bridge input terminal, an inverted bridge input terminal, a clock terminal and an inverted clock terminal. The modulator further comprises an input amplifier for amplifying an input signal and an inverted input signal and a bridge amplifier coupled to the input amplifier. The bridge amplifier is also coupled to the bridge. The modulator further comprises a feedback amplifier coupled to the bridge and the bridge amplifier, and a clock amplifier for amplifying a clock signal and an inverted clock signal. The bridge is coupled to the clock amplifier. An output signal is present at an output terminal that is coupled to the bridge input terminal. An inverted output signal is present at an inverted output terminal coupled to the inverted bridge input terminal.
Technical advantages of the present invention include providing an improved system for continuous-time modulation. In particular, a negative-resistance device such as a resonant tunneling diode is utilized in the implementation of the continuous-time modulator. Accordingly, reliance on transistors is avoided. As a result, quantum mechanical effects are not detrimental, the switching speed is increased, and the use of multi-valued logic is made possible.
Other technical advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions, and claims.